Hat-based oximeter sensor

ABSTRACT

A method for use and an improved oximeter sensor substrate that is conforming to the shape of the patient&#39;s forehead. In one embodiment, the present invention is an oximeter sensor, having a substrate with a shape similar to a shape of at least a portion of a patient&#39;s forehead and including a section adapted to substantially fit over a portion of a forehead of a patient; an emitter disposed on the substrate at a position located on the section; and a detector disposed on the substrate at a distance from the emitter. In one embodiment, the substrate includes a hat that holds the emitter and the detector in a spaced-part manner against the patient&#39;s forehead.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/358,868 filed Feb. 21, 2006, the specification of which is herebyincorporated by reference in its entirety, which is a divisional ofprior U.S. application Ser. No. 10/606,668, filed Jun. 25, 2003, nowU.S. Pat. No. 7,047,056 issued May 16, 2006, the specification of whichis incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical oximeter sensors, and inparticular to hat-based pulse oximeter sensors.

Many types of optical sensors are used to measure physiologicalcharacteristics of a patient. Typically, an optical sensor providesemitted light which is then scattered through a portion of a patient'stissue and detected. Various characteristics of a patient can bedetermined from analyzing such light, such as oxygen saturation, pulserate, tissue bilirubin, etc.

Pulse oximetry is typically used to measure various blood flowcharacteristics including, but not limited to, the blood-oxygensaturation of hemoglobin in arterial blood, the volume of individualblood pulsations supplying the tissue, and the rate of blood pulsationscorresponding to each heartbeat of a patient. Measurement of thesecharacteristics has been accomplished by use of a non-invasive sensorwhich scatters light through a portion of the patient's tissue whereblood perfuses the tissue, and photoelectrically senses the absorptionof light in such tissue. The amount of light absorbed is then used tocalculate the amount of blood constituent being measured.

The light scattered through the tissue is selected to be of one or morewavelengths that are absorbed by the blood in an amount representativeof the amount of the blood constituent present in the blood. The amountof transmitted light scattered through the tissue will vary inaccordance with the changing amount of blood constituent in the tissueand the related light absorption. For measuring blood oxygen level, suchsensors have typically been provided with a light source that is adaptedto generate light of at least two different wavelengths, and withphotodetectors sensitive to both of those wavelengths, in accordancewith known techniques for measuring blood oxygen saturation.

Known non-invasive sensors include devices that are secured to a portionof the body, such as a finger, an ear or the scalp. In animals andhumans, the tissue of these body portions is perfused with blood and thetissue surface is readily accessible to the sensor.

Certain types of oximeter sensors are applied to a patient's forehead.To aid in the sensor's proper placement and the proper application ofpressure by the sensor to the forehead site, some forehead sensors aremaintained at the forehead site by either the assistance of an adhesivelayer and/or a headband. While these approaches are helpful, there isstill a need for an improved and easy way of placing, retaining, andlocating the sensor on the forehead of its user.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an oximeter sensor which will attach to apatient's forehead in an improved manner. In certain embodiments, thesecuring of the sensor to the forehead of the patient is achieved byattaching the sensor to the inside of hat which is worn by the patientwhen the sensor is in use.

In one embodiment, the present invention is an oximeter sensor, having:a substrate having a shape similar to a shape of at least a portion of apatient's forehead and including a section adapted to substantially fitover a portion of a forehead of a patient; an emitter disposed on thesubstrate at a position located on the section; and a detector disposedon the substrate at a distance from the emitter.

In one embodiment, the substrate is resilient and has a shapeconformable to the forehead of a patient.

In one embodiment, the substrate includes an adhesive layer for adheringto the forehead of a patient.

In one embodiment, a hat is used for holding the sensor against thepatient's forehead.

In one embodiment, the substrate is adhered to the inside of said hat.

In one embodiment, the substrate is adhesively attached to the inside ofthe hat. Alternately, the substrate is sewn into the hat.

In another embodiment, the present invention provides a method fordetermination of a blood characteristic, including: applying an emitterand a detector to spaced-apart positions on a forehead of a patient inthe lower forehead region, above the eyebrow, with both the detector andthe emitter placed above and predominantly lateral of the iris; securingthe emitter and detector to the patient; emitting electromagneticradiation with the emitter; detecting electromagnetic radiationscattered by the tissues of the forehead by the detector and producing adetector signal; and determining a blood characteristic in the patientfrom the detector signal.

In one embodiment, the securing of the emitter and the detector to thepatient's forehead is achieved by attaching the emitter and the detectorto an inside of a hat, and placing the hat on the head of the patient.

For a further understanding of the nature and advantages of the presentinvention, reference should be made to the following description inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembly drawing of an embodiment of the sensor inaccordance with the present invention that can be placed within a hat orcap.

FIG. 2 is a drawing of a stocking hat, with an embodiment of the sensorin accordance with the present invention shown mounted in the hat.

FIG. 3 is an assembly drawing of an embodiment of the sensor of FIG. 1or 2.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention are directed towardsconfiguring a reflectance-type oximeter sensor for placement in a hat inorder to provide a relatively easy means of placing, retaining, andlocating the sensor on the forehead of the user. With regard to thelocation of the sensor on the patient's forehead, it is preferred tohave the sensor be located on the lower forehead region, above theeyebrow, with the sensor optics (emitter and detector) located above andpredominantly lateral to or centered over the iris. The oximeter sensorcan be attached to the inside band of a hat. The precise location of thereflectance sensor in the hat allows appropriate placement of the sensorin the optimal forehead location by a user not skilled in sensorplacement. It has been found that the placement of a reflectanceforehead sensor is a factor in the accurate determination of a bloodflow characteristic, due to the vasculature of the forehead. Inaddition, it has been shown that having a certain amount of pressure onthe forehead sensor can reduce the incidence of venous pulsationseffects on the oximeter reading. The placement of the sensor in the bandof the hat would minimize these issues, as the placement of a hat isfairly repeatable and predictable. A hat-based oximeter sensor asembodied by the present invention can be used on patients in clinicalsettings, or by athletes, soldiers, firemen, or in any environment whereinformation related to a physiological parameter, such as heart rate oroxygen saturation information is desired.

FIG. 1 is an assembly drawing of an embodiment of the sensor inaccordance with the present invention that can be placed within a hat orcap. This figure shows an oximeter sensor placed on a substrate 102 thatcan be placed or adhered to the inside of a hat 104. In the hat-basedembodiment, the sensor uses an emitter 106 containing two discretewavelengths and a detector 108 placed more than 2 mm away, and ideally10 mm-15 mm from the emitter. The surface 102 can be black in order tominimize any shunting of light between sensor and patient skin. Thesensor in a hat could be used in conjunction with a small, portableoximeter to allow mobility of the user during activities. Similarly, thesensor could be incorporated into a headband. Alternately, it may bedesirable to provide a sensor with adhesive backing that would allow theuser to place the sensor in a hat of their choice. Also shown in FIG. 1is a cable 110 for providing drive current to the LED and for providingthe detector signal to the oximeter. The cable provides the electricalconnection to the monitor; it also provides power for the emitter,signal carrying conductors from the detector, and shielding to protectthe small signals from the detector against external electricalinterference.

The sensor is shown in a multi-layer structure having a face portion112. The face 112 is the surface that is placed against the patient'sskin. The face material may have an adhesive layer such as an acrylic orsynthetic rubber adhesive, or it may be without adhesive, and typicallymade from a foam PVC or foam polyurethane material. The face 112component is preferably black so as to minimize the incidence ofreflected light that does not go through the tissue. Below the facelayer 112 are two windows 114. The windows 114 are generally a clearcomponent, such as for example, a thin film or a clear molded plasticcomponent that makes contact with the skin. The thin film window may bea polyurethane or an acrylic adhesive on a polyester film. The intent ofthe window 114 is to provide an efficient optical coupling mechanismbetween the optical components (emitter and detector) and the skin.Located above the face 114, is a Faraday shield 116. The Faraday shield116 is a conductive material, for example, a copper film or copper mesh,that is electrically connected to the monitor ground to help shield thedetector from extraneous electrical interference while passing light tothe detector. Next located are the LED 106 and the detector 108. Abovethe LED and the detector is a mask layer, which may include more thanone mask layer. The mask layer 118 is generally a thin film that isintended to block light from entering the back side of the sensor, orfrom traveling directly from emitter to detector (shunt light). Thepurpose of the mask 118 is to ensure that all of the light reaching thedetector is light from the emitter that has traveled through thecapillary bed. Above the mask layer 118 is the back layer 120. The backor the top layer is the non-tissue contacting surface of the sensor.This layer may include a cosmetic finish for the sensor, which can bewhite with some printed artwork identifying the sensor. Typicalmaterials may be Velcro loop, or soft PVC foam. In a case where thesensor is mounted inside a hat or cap, the top layer is sometimesreferred to as the back layer. In this case, the back layer may includea double stick adhesive so that it can be mounted inside the hat.

FIG. 2 shows a stocking hat, with an embodiment of the sensor inaccordance with the present invention shown mounted in the hat. Thisalternate embodiment of the present invention, is directed towards theplacement of a small reflectance sensor 202 in a stocking cap or beanie204. FIG. 2 shows the sensor carrier layer 202 holding an LED 206 and adetector 208 and a cable 210, similar to the ones described above inconjunction with FIG. 1. This embodiment may be used for neonates. Thisembodiment would allow easy placement of a sensor on the forehead of apatient while applying a predictable pressure on the sensor. The sensorin a hat also resolves a concern about the cosmetic appearance of havinga sensor on the forehead of the patient. A sensor in a stocking cap ismuch more acceptable to a parent than having a sensor located on theforehead. Depending on the tension of the stocking cap, provided by itsown stretchiness or by an adjustable integral headband strap, the sensormay have a light tack adhesive, or no adhesive at all. The lack of anadhesive layer is a desirable feature, especially on neonates asadhesives may sometimes leave visible damage to the fragile skin of aneonate.

FIG. 3 is an assembly drawing for an embodiment of the sensor of FIG. 1or 2. FIG. 3 shows that the sensor portion generally includes a facelayer 302, a top layer 304 and a flex circuit 306 that is placed betweenthe face and top layers. Also shown in FIG. 3 is a multi-layerunassembled view showing the relative positions of the face 302, flexcircuit 306, a cable 308 and the top layer 304. The flex circuit layer306 holds the emitter (LED) 310 and the detector 312 as well as the masklayer 314 and Faraday shield as described above. The flex circuit 306also has several holes 316 to allow for electrical connections betweenthe leads in the cable and the LED and the detector.

As will be understood by those skilled in the art, the present inventionmay be embodied in other specific forms without departing from theessential characteristics thereof. For example, the sensor may includeadhesive layers for adhering to the inside of a hat or the user's skin,or that that the sensor may be sewn into the hat. These otherembodiments are intended to be included within the scope of the presentinvention, which is set forth in the following claims.

1. A sensor comprising: a stocking cap; a substrate disposed on thestocking cap; and at least one sensing component disposed on thesubstrate, wherein the sensing component is adapted to be located in alower forehead region when the stocking cap is applied to a patient. 2.The sensor of claim 1, wherein the substrate is conformable to aforehead-contacting surface of the stocking cap.
 3. The sensor of claim1, wherein the substrate comprises an adhesive layer adapted to attachthe substrate to the stocking cap.
 4. The sensor of claim 1, wherein thestocking cap comprises a neonatal stocking cap.
 5. The sensor of claim1, wherein the stocking cap comprises an opening adapted to accommodatethe sensor.
 6. The sensor of claim 7, wherein the opening comprises ahole or a pocket.
 7. The sensor of claim 1, comprising an electricalconnector extending from the substrate through an open portion of thestocking cap when the stocking cap is applied to the patient.
 8. Thesensor of claim 1, wherein the sensing component comprises at least oneof an emitter or a detector.
 9. The sensor of claim 1, wherein thestocking cap comprises one or more alignment indicia for aligning thesubstrate to the lower forehead region.
 10. The sensor of claim 1,wherein the sensing component is adapted to be centered substantiallyabove the patient's iris when the stocking cap is applied to thepatient.
 11. A method of manufacturing a cap-based sensor comprising:providing a stocking cap; providing a substrate, and providing at leastone sensing component disposed on the substrate, wherein the sensingcomponent adapted to be located in a lower forehead region when thestocking cap is applied to a patient.
 12. The method of claim 11,wherein the substrate is conformable to a forehead-contacting surface ofthe stocking cap.
 13. The method of claim 11, comprising providing anadhesive layer adapted to attach the substrate to the stocking cap. 14.The method of claim 11, wherein the stocking cap comprises a neonatalstocking cap.
 15. The method of claim 11, comprising providing anopening adapted to accommodate the sensor.
 16. The method of claim 15,wherein the opening comprises a hole or a pocket.
 17. The method ofclaim 11, comprising providing an electrical connector extending fromthe substrate through an open portion of the stocking cap when thestocking cap is applied to the patient.
 18. The method of claim 17,wherein the at least a portion of the electrical connector comprises acable.
 19. The method of claim 11, wherein the sensing componentcomprises at least one of an emitter or a detector.
 20. The method ofclaim 11, wherein the sensing component is adapted to be locatedsubstantially centered above a patient's iris when the stocking cap isapplied to the patient.
 21. A method of applying a sensor comprising:applying a stocking cap to a patient, wherein the stocking cap comprisesa substrate and at least one sensing component disposed on thesubstrate; and aligning the sensing component to a lower forehead regionwhen the stocking cap is applied to the patient.
 22. The method of claim21, wherein the sensing component comprises at least one of an emitteror a detector.
 23. The method of claim 21, wherein the substrate isconformable to a forehead-contacting surface of the stocking cap. 24.The method of claim 21, wherein the stocking cap comprises an adhesivelayer adapted to attach the substrate to the stocking cap.
 25. Themethod of claim 21, wherein the stocking cap comprises a neonatalstocking cap.
 26. The method of claim 21, wherein the stocking capcomprises an opening adapted to accommodate the sensor.
 27. The methodof claim 26, wherein the opening comprises a hole or a pocket.
 28. Themethod of claim 21, wherein the stocking cap comprises an electricalconnector extending from the substrate through an open portion of thestocking cap when the stocking cap is applied to the patient.
 29. Themethod of claim 21, wherein the at least a portion of the electricalconnector comprises a cable.
 30. The method of claim 21, comprisingaligning the sensing component to a position substantially centeredabove a patient's iris.